Generally, when output of a power amplifier circuit (power amplifier) that amplifies an audio signal is supplied to a speaker, an offset detection circuit may be adopted for removing a DC offset in the output of an amplifier in order to prevent damage to the speaker.
However, the offset detection circuit in the related art cannot detect the DC offset at the time of audio reproduction (at the time of presence of signal), but can detect the DC offset only when there is no signal such as when an audio set is activated, and thus the damage of the speaker may not be reliably prevented.
Even in the related art, an offset detection circuit can detect the offset at the time of the presence of the signal. However, there is a problem that a low pass filter having a large time constant or a DC shift circuit is required.